Original ideas wanted for possible project...

[Mugs914]

I'm starting this thread because of all of the really cool and creative ideas you guys mentioned over on the rail guide thread. I'm hoping to tap into that creative spirit here, so any thought or idea is welcome. Kind of a like a virtual brainstorming session!

I have long been fascinated by the Sprint ABM from the '60s/early '70s. If you aren't familiar with it, you can check this link for more info. I was truly a remarkable piece of work!

Years ago, I built many versions of the Sprint. From a tiny 13mm version to a three-plus foot, 24mm version, all were pretty good flyers and were fun for a number of reasons, not least of which was that they were finless. The LPR versions were relatively easy to get on the launch rod because they all featured a regular type launch lug mounted to the core tube with a hole near the nose for the rod to pass through. (See pics below of my one surviving LPR Sprint)

Recently I've started toying with the idea of an HPR version of the Sprint and have done a very preliminary OR file for a 73" by 12" diameter, 54mm motor version (see attached). Its all pretty straight forward until it comes to launching the thing. I suppose I could just go old-school and use 1/2" diameter launch lugs on the inner tube, but it seems a bit inelegant and who uses half-inch launch rods anymore? I would like to use a rail, but of course that would put the thing on an angle coming off the rail. That might not matter much in the overall scheme, but why invite potentially rowdy guests to the party?

I have several ideas rattling around in my head, none that are really jumping out though. I thought about tube launching like the original, but a cone-shaped rocket pushing sabot up the pipe just seems like a great way to jam the thing in the tube. S'pose it could be made to work, though...

Anyway...

I thought the collected brain power of the forum might be willing to give this problem a moment's thought and might have a little fun doing it.

Like I said, all ideas are welcome (serious or not!).

Thanks in advance!

Mike

LPR Sprint. 25 years old and a bit rough, but still flies:

Launch lug just visible...


OR file for HPR version. Very basic, but gives a place to start the design.

 

[lr64]

This might be a good candidate for a customized flyaway rail guide, as described on the Apogee site. Maybe even something u-shaped that comes in from the bottom. However, I wonder if launching slightly skewed is really that much of a problem. One could also imagine retractable struts with rail guides on them, but that seems like it might be trickier.


BTW, the shape of the rocket makes me think of the band Le Snob performing on Segways. Video of them performing that way can be found on line, and I think it's highly amusing.

 

[Art Upton]

Mine was an ARF from Shadow Aero. Like yours it uses a Rod thru the cone. Mine has not flown. Probably will not, but who knows.

 

[Rschub]

Well, there is this...
https://www.rocketryforum.com/threads/sprint-abm-build-thread.174473/
I plan on having the rail go through one of the openings that will provide some stabilization. It won't exactly be a Sprint scale model that way though.

You could also use a launch tube as in the original, the fin tip is right at the diameter of the base, with a tiny bit of tweaking. I wonder if you would get a smoke ring launching it that way.....

 

[SDramstad]

Could you put a rail button on the fin tip? would that be straight enough?

and with the motor recessed that far is the Krushnic effect going to be a problem?

A 6 inch diameter version with an H999 Warp 9 motor would be fun

 

[mikec]

For some tests it was launched off a rail, so you have a scale example (got this off the other thread.)

 

[ReynoldsSlumber]

For some tests it was launched off a rail, so you have a scale example (got this off the other thread.)

Wow, those rails are so short, about as long as a low power model rocket launch rod! I knew the acceleration was absurd, but dang. Interesting how they're staggered so that both rail guides come off the rail simultaneously, no binding there. Might those be flyaway rail guides?

 

[Rschub]

I think in this in-flight picture you can see the extended rail guide and the umbilical connection from the above picture.

I think the motor produced 100 G of acceleration in turning, and up to 600 G in a straight line according to some sources.

 

[lr64]

That's a great shot. How do you even build anything that can take 600g?

 

[teepot]

If tube launched you could use spring steel wire with a slight bend at the ends to act as guides for the upper smaller diameter part of the rocket. I've been thinking of doing that with a rocket I want to tube launch instead of forward fins.

 

[KenECoyote]

Want an original idea? How about a spring loaded lever with a rail button on the end that flips up into the body after it leaves the rail?

Of course this would be very tricky to do, but I can envision it working if done right (make sure lever is very strong, has a stiff enough bottom stop to prevent hanging up as well as a strong enough spring).

 

[Steve Shannon]

I would be tempted to simply put it in a tower. Farther out at first.

 

[OverTheTop]

I was also thinking tower.

Or maybe a piston launcher?

 

[Art Upton]

I was also thinking tower.

Or maybe a piston launcher?

I'm curious, do AP composite motors have any trouble with Piston Launchers?

Someone somewhere talked about it when AP motors became common and I can't remember much about the outcome. Have you seen it done with no issues? If so that would be Kewl.

 

[OverTheTop]

I have never seen a piston launcher used. Only read about them.

 

[gb1113]

Wish I could find my documentation on this one (early 2000's ?? Brothers Designs perhaps?). I think I launched it twice and it flew well on a D, but last flight burned out the Kevlar liner. The outer detail sheet was attached to the inner paper form with spray adhesive - and I missed my alignment by a bit. Launch instructions were to angle rod at 2 degrees from vertical.
Seems for a HP version you would need a motor with very high initial impulse. I'd go with the forward standoff solidly attached to the main motor tube. Not sure how aft launch lug point would be anchored since extra weight aft is not going to help stability at all.
The link RSCHUB provided to a previous build is really interesting. Given the HP motor may have to mount well forward in the tube - keeping the lower portion of the cone from burning off is no small trick.

 

[Sooner Boomer]

I've got a project very similar to yours. I've got a Hobby Lobby paper mache cone that's 21" tall, and 6" in dia. My plan is to tube launch it. I've got a 6' cardboard tube that is a perfect fit. I plan on using triangular foam pieces to keep the cone centered in the tube as it is launched. see; https://www.rocketryforum.com/threads/the-very-draggy-rocket-a-thought-experiment.46191/post-445983

 

[teepot]

The orange landscape flags I have are spring steel and can be bent to make the end rounded. I saw a video of a guy that tube launches a lot of his rockets and he used a flexible wire with a rounded end that made it look like his rockets had whiskers to keep them entered in his tube launcher. That's where I got the idea.

 

[boatgeek]

Here’s an out of the box idea: tube launch. To keep the rocket centered, make a foam plug that matches the ID of the tube and fits snugly over the rocket. Split the plug lengthwise into 3 or 4 sections that will fall away when the rocket clears the tube.

It’s possible that the rocket will wedge the plug out and cause too much drag. You might be able to solve that by really reducing friction in the outside of the plug or by adding a wrap of scotch tape at the top and bottom to keep the plug from expanding. If you do the latter, you’ll need a couple of small blades to cut the tape as the plug leaves the tube.

 

[Capt. Eric]

I built and flew a Christmas tree rocket that is similarly shaped. (Flew well... Until an E12 blew it apart) It is made from remains of an Extreme 12 main body, DRM nose cone, and poster board wrapped into 2 cones, 1 attached to the nose cone. Holes drilled into the centering rings lined up to the launch lugs and allowed up to a 3/16" rod (it flew on a 1/8" rod too). You could possibly do this with 2 1/4" rods, one on each side. You'd have to make a launch arrangement that holds 2 rods parallel at the same distance apart as the rocket has holes for. If not, a really large opening that allows a rail to pass through. Would a micro button rail be stiff enough, and not too obtrusive?

 

[Mugs914]

Could you put a rail button on the fin tip? would that be straight enough?

I thought about that, but I'm trying to really do a scale version, so I'd like to keep things as accurate as possible. Still a good option though...

and with the motor recessed that far is the Krushnic effect going to be a problem?

Never has been with any of my previous iterations. Just kept them up away from the deflectors or used an angled deflector.

A 6 inch diameter version with an H999 Warp 9 motor would be fun

I had just that very thing simmed up in OR but lost it (and a bunch of other OR stuff) in a computer crash. As I recall, it maxed at Mach 1.04 or something with an apogee at 1700 feet.

Definitely going to re-do that one in OR. Sure would be a spectacular flight!

Edit:

Just re-did the OR sim for a 39.6" OAL, 6" diameter version on an H999:

Max. vel. - 784 mph (Mach 1.03)
Apogee - 1799 ft.
Velocity off 6' rail - 164 mph
Motor burnout at 220 ft.
Max. acceleration - 179 G.